Greenwood, 42, had built up a reputation as an exceptionally talented book dealer. He had bought and sold early editions of Harry Potter (one of which was stolen from an art gallery in Woodstock) and came to media attention following the sale of a rare piece by Banksy in 2011.

Featuring unprecedented access to the Thames Valley Police Major Crime Unit, the programme follows the investigation led by Detective Superintendent Kevin Brown and his team.

Thames Valley Police
Michael Danaher was jailed in October&nbsp;

Jobless Michael Danaher, of Peterborough, was drowning in £13,000 of debt. At 25 stone, he was obese, suffering from severe diabetes and had recently separated from his wife.

So it was no surprise that Greenwood’s rare copy of The Wind In The Willows was what drew him into Danaher’s desperate orbit.

A post-mortem examination found Greenwood died from multiple “savage” stab wounds to the chest and neck and that he had defensive wounds to his hands.

He was stabbed in the back, stamped on until his right arm was broken and left for dead, the jury heard. At the time of his death he had more than 2,000 items for sale, 17 of which were worth more than £2,000 each.

Frederick Hollyer via Getty Images
A rare first edition of Kenneth Grahame&rsquo;s 1908 children&rsquo;s book The Wind In The Willows&nbsp;was the motivation for the crime&nbsp;

One of the stab wounds penetrated 10cm, while 30 puncture injuries caused by a knife tip indicated the victim may have been tortured for information - likely as to the whereabouts of the valuable book . The handle of the knife was found not far from Greenwood’s body, the blade presumably broken off.

Danaher, who took a selfie of his bloodied face on the doorstep of Greenwood’s home, was arrested days later. Among the evidence found linking him to the crime was the blade of the knife used to stab Greenwood, a pair of bloodied boots and a stun gun made to look like an iPhone.

Greenwood’s phone was taken during the attack, later to be traced to Peterborough on the day of the murder. Number plate technology revealed the only car that travelled through Oxford to Peterborough that day was a Citroen Picasso belonging to Danaher.

The killer advertised the stolen book on eBay the very next day.

Later in court it emerged the 50-year-old former John Lewis worker had compiled a spreadsheet of high-profile figures including Jeffrey Archer and Kate Moss as potential targets for extortion. Greenwood’s name was found on the list.

Danaher denied murder, claiming he acted in self-defence after Greenwood came at him with a knife and called him an “obese tosser” when he visited the property to buy some books. He told the court Greenwood was stabbed in the scuffle.

Following a trial in October, the father-of-two was convicted of murder and sentenced to 34 years imprisonment.

Catching A Killer: The Wind In The Willows Murder will air on Channel 4 at 9pm on Monday 10 July.